The long-term goal of this project is to further basic knowledge in the area of cholesterol biosynthesis and its regulation. This information should aid in the prevention and treatment of arteriosclerosis and related cardiovascular diseases. In particular, studies on the squalene and sterol carrier protein (SCP) will be continued, e.g. to determine the structural relationships of SCP to serum lipoproteins and possible role of SCP in the regulation of lipid biosynthesis and metabolism. The effects on SCP levels and activities of physiological conditions known to alter lipid metabolism in vivo will be examined. The structural characteristics of SCP and mechanisms of lipid binding to SCP will be elucidated using physical-chemical techniques. The studies will be carried out on human as well as animal tissues and cultured cells. The occurrence and role of SCP in lower forms of life, e.g. yeast, protozoa, will also be determined.